The universal swivel joint has achieved widespread acceptance in electrical apparatus, and most commonly, such swivels are utilized to permit the extensive angular adjustment of a light source supported on a suitable base. Assuming a fixed base, the swivel normally allows rotation of the light source slightly less than 360.degree. about one axis, and about 180.degree. about a perpendicular axis. Thus, the illumination may be directed in almost any desired manner.
Perhaps the most widely accepted electrical swivel consists of a white metal device comprised of four principal diecastings, two of which form an elongated hollow central body portion, while a base element and a tiltable upper element are clamped between the two body sections. The flexible insulated electrical wire passes upward through the base, between the two body sections and out through the tiltable upper component. While low cost has undoubtedly been a principal factor in the success of this swivel, numerous disadvantages are known; most significantly, their inability to survive effectively in corrosive atmospheres, their poor performance under shock and vibration and that continued tilt and turn may ultimately cause the insulation of the internal wire to fray within the case metal housing and cause an electrical short circuit. Further, operation which is less than smooth is to a large extent dependent upon the tightness of the assembly screws.
The patent literature is quite illustrative of prior swivel designs, and U.S. Pat. Nos. 2,587,917, 2,887,329 and 3,091,484 are illustrative of relevant advances in the art. There are, of course, numerous other patents in the related Patent Office class which show not only earlier designs but also efforts to enhance the utility and ease of manufacture of the product. These patents furnish useful background, and a study thereof is advantageous to an understanding of the features and advantages of the present invention.